To determine the percent composition of ethanol, we need to determine the weight of each element from ethanol.

We'll write the chemical formula of ethanol: C2H5OH.

To calculate the weight of each element, we need to know how many moles of each element ethanol has. This thing could be easy determined just looking at the subscripts of each constituent element. Therefore ethanol has : 2 mols of carbon, 1 mole of oxygen and 6 mols of hydrogen.